Light emitting semiconductor device and method of manufacture thereof

ABSTRACT

The light emitting device has a substrate, metallization including silver established on the surface of the substrate, a light emitting element mounted on the substrate, conducting wire that electrically connects the metallization and the light emitting element, light reflective resin provided on the substrate to reflect light from the light emitting element, and insulating material that covers at least part of the metallization surfaces. The insulating material is established to come in contact with the side of the light emitting element. This arrangement can suppress the leakage of light emitting element light from the substrate, and can achieve a light emitting device with high light extraction efficiency.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light emitting device that can beused in applications such as an indicator device, lighting equipment,display monitor, or backlight source for a liquid crystal display, andto the method of manufacturing the light emitting device. Moreparticularly, the present invention relates to a light emitting deviceand its method of manufacture that has exceptional light extractionefficiency as well as high reliability.

2. Description of the Related Art

In recent years, various light emitting devices such as light emittingdiode (LED) and laser diode (LD) apparatus that employ high outputsemiconductor light emitting elements (also referred to below simply aslight emitting elements) have been developed.

Recently, an assortment of electronic components have been proposed anddeveloped, and demands on their performance has also increased. Inparticular, long-term, stable performance is demanded even in harshoperating environments. Similarly, for light emitting devices beginningwith light emitting diodes, performance demands in fields such asgeneral lighting and automotive lighting are increasing daily, and highoutput and high reliability are particularly in demand. Furthermore,supply of these devices at low prices while maximizing their performanceis required.

In general, a light emitting device has a substrate that carrieselectronic components such as semiconductor light emitting elements(also referred to below as light emitting elements) and protectiondevices, and conducting material to supply electrical power to thoseelectronic components. Further, the light emitting device haslight-transparent encapsulating material to protect the electroniccomponents from the outside environment.

To achieve high output, the output of the employed light emittingelements themselves can be increased. In addition, it is effective toimprove the light extraction efficiency via the materials andconfiguration of components such as the substrate, the conductingmaterial, and the encapsulating material.

For example, high conductivity metals are used as the conductingmaterial, and the surface of the conducting material can be plated withsilver to efficiently reflect light from the light emitting elements.Further, resin that easily passes light from the light emitting elementsis appropriate as the encapsulating material. Among those resins,silicone resin, which has excellent heat durability and is able towithstand harsh environments (weather-ability), can be used in an effortto increase apparatus lifetime.

However, silver has the tendency to degrade easily due to atmosphericconstituents such as sulfur. Accordingly, Japanese Laid-Open PatentPublication No. 2004-207258A discloses use of an organic agent toprevent silver discoloration. In addition, Japanese Laid-Open PatentPublication No. 2006-303069A discloses plating the silver with a noblemetal, and Japanese Laid-Open Patent Publication No. 2007-324256Adiscloses a sol-gel glass coating.

In addition, light emitting devices that carry not only light emittingelements, but also carry electronic components such as Zener diodes orsubmounts have been developed. As a result, high reliability, longlifetime light emitting devices are possible. Since these other types ofelectronic components can easily absorb light from the light emittingelements, a reflective layer can be provided that covers thosecomponents and reduces light loss (see for example, Japanese Laid-OpenPatent Publication No. 2005-26401A).

However, in the case of organic material covering silver, environmentalresistance is problematic and the system can easily degrade over time.For noble metal plating, although environmental resistance is not aproblem, noble metals have lower reflectance than silver and initialreduction in output is unavoidable.

Further, the thickness of sol-gel glass coating is difficult to control,mass production is problematic, and as a result cost is an obstacle.

The present invention was developed considering these types of problemswith the prior art. Thus, it is a primary object of the presentinvention to suppress the degradation of silver used in metallizationfor electrodes, and to provide a high output, high reliability lightemitting device and method of manufacture.

SUMMARY OF THE INVENTION

To achieve the object described above, a light emitting device for thefirst aspect of the present invention has a substrate, metallizationthat has metal including silver established on the surface of thesubstrate, light emitting elements mounted on the substrate, conductingwire that electrically connects the metallization and the light emittingelements, light reflective resin provided on the substrate to reflectlight from the light emitting elements, and insulating material thatcovers at least part of the metallization surfaces. In addition, theinsulating material can be provided to contact the sides of the lightemitting elements.

In addition, a light emitting device manufacturing method for anotheraspect of the present invention can include a process step to provide asubstrate that has a first cavity, and second cavities inside the firstcavity with bottom surfaces positioned below the first cavity; a processstep to provide metallization on the upper surface of the substrate; aprocess step to provide light emitting elements on top of themetallization and connect the metallization and light emitting elementswith conducting wire; a process step to cover continuously withinsulating material the surfaces of metallization on the bottom surfacesinside the second cavities, the side-walls joining the first and secondcavities, the surface of metallization in the first cavity, surfaces ofthe light emitting elements, and the conducting wire; and a process stepto provide light reflective resin in the second cavities to reflectlight from the light emitting elements.

In this manner, leakage of light from the light emitting elementsthrough the substrate can be suppressed to obtain a light emittingdevice with high light extraction efficiency. In particular, leakage oflight from the light emitting elements through the substrate can beprevented, light reflective resin can be provided near the lightemitting elements to efficiently reflect light, and silver degradationcan be effectively suppressed to attain a light emitting device withimproved light extraction efficiency. Further, when protection devicesand conducting wire are used, light absorption by those components canbe suppressed to obtain a light emitting device with little light loss.

The above and further objects of the present invention as well as thefeatures thereof will become more apparent from the following detaileddescription to be made in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an oblique view showing a light emitting device for the firstembodiment of the invention;

FIG. 1B is a cross-section view through IB-IB′ on the light emittingdevice of FIG. 1A;

FIG. 2A is an oblique view showing a light emitting device for thesecond embodiment of the invention;

FIG. 2B is a top view showing the inside of the light emitting device ofFIG. 2A;

FIG. 2C is a cross-section view through IIC-IIC′ on the light emittingdevice of FIG. 2A;

FIG. 3 is a cross-section view of a light emitting device for the thirdembodiment of the invention;

FIG. 4 is a cross-section view of a light emitting device for the fourthembodiment of the invention;

FIG. 5 is a cross-section view of a light emitting device for the fifthembodiment of the invention; and

FIG. 6 is a cross-section view of a light emitting device for the sixthembodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENT(S)

In the light emitting device, the substrate can have cavities withside-walls and bottom surfaces, the cavities can have a first cavitywith light emitting elements attached and second cavities inside thefirst cavity having bottom surfaces positioned below the first cavity,and light reflective resin can be provided on metallization inside thesecond cavities.

Further, side-walls that join the second cavities to the first cavitycan be covered with insulating material.

Still further, light reflective resin can extend upward from the secondcavities to a position above the first cavity.

Still further, the light emitting device can have a substrate,metallization that has metal including silver established on the surfaceof the substrate, light emitting elements mounted on the substrate,conducting wire that electrically connects the metallization and thelight emitting elements, light reflective resin provided on thesubstrate to reflect light from the light emitting elements, andinsulating material that covers at least part of the metallizationsurfaces. In addition, the insulating material can be providedcontinuously over the upper surfaces of the metallization and the lightemitting elements. In this manner, light leakage from the light emittingelements through the substrate can be suppressed and a light emittingdevice with high light extraction efficiency can be produced. Inparticular, since leakage of light from the light emitting elementsthrough the substrate can be prevented, since light reflective resin canbe provided near the light emitting elements to efficiently reflectlight, and since silver degradation can be effectively suppressed, alight emitting device with improved light extraction efficiency can beproduced. Furthermore, when conducting wire and protection devices areused; light absorption by those components can be suppressed to easilyrealize a light emitting device with minimal light loss.

Still further, the insulating material can be provided between themetallization and the light reflective resin, and that insulatingmaterial can extend continuously over the upper surfaces of the lightemitting elements.

Still further, the insulating material can be provided on the surface ofthe light reflective resin, and that insulating material can extendcontinuously over the upper surfaces of the light emitting elements.

Still further, the insulating material can be provided over the uppersurfaces of the light emitting elements and extend to cover the surfacesof the conducting wire.

Still further, essentially the entire upper surface of the substrate canbe covered by the insulating material.

Still further, encapsulating material can be provided to enclose thelight emitting elements, essentially all of the conducting wire, and atleast part of the insulating material on the upper surface of thesubstrate.

Still further, the insulating material can have light-transparentproperties.

Still further, the insulating material can be an inorganic compound.

Still further, the insulating material can be SiO₂.

Still further, the light emitting elements are mounted on top of themetallization and the metallization can function as electrodes.

First Embodiment

The following describes embodiments of the present invention based onthe figures. First, FIGS. 1A and 1B show a light emitting device 100 forthe first embodiment. FIG. 1A is an oblique view of the light emittingdevice 100, and FIG. 1B is a cross-section view through IB-IB′ on thelight emitting device 100 shown in FIG. 1A. In this embodiment, thelight emitting device 100 has an approximately rectangular substrate 101with metallization 103A, 103B, 103C disposed on its upper surface, and aplurality of light emitting elements 104 mounted on the metallization103A established on the upper surface of the substrate 101.Metallization 103A, 103B used as electrodes and the light emittingelements 104 are directly or indirectly connected electrically viaconducting wire 105. Although metallization 103C is the same material asmetallization 103A, 103B, which act as electrodes, it is not anelectrically connected component, and is provided as a marker (cathodemark, anode mark) indicating the polarity of the light emitting device.

In the present embodiment, light reflective resin 102 is provided aroundthe light emitting elements 104 to reflect light from the light emittingelements, insulating material 107 is established between themetallization 103A, 103B and the light reflective resin 102, and theinsulating material 107 is established to extend continuously over thetops of the light emitting elements 104. Further, the inside of thecavity formed by side-walls of the light reflective resin 102 is filledwith light-transparent encapsulating material 106 to protect componentssuch as the light emitting elements 104 from the external environment.As a result of this structure, degradation of the silver plating on themetallization can be suppressed by the insulating material, and lightthat could leak through the substrate via regions between the positiveand negative electrodes, where structurally silver cannot beestablished, can be efficiently reflected by the light reflective resin.

(Light Reflective Resin)

The light reflective resin is a material that can efficiently reflectlight from the light emitting elements. As shown in FIGS. 1A and 1B, thelight reflective resin 102 is established in a manner that surrounds thelight emitting elements 104. The light reflective resin 102 isestablished in a manner that covers part of the metallization 103A,103B. Insulating material 107 is established between the metallizationand the light reflective resin, and extends continuously over the lightemitting elements 104. This type of structure can easily be obtained bymounting the light emitting elements on the metallization, establishinginsulating material 107 over the entire substrate 101, and subsequentlyforming the light reflective resin 102. In this manner, since insulatingmaterial can be established even on top of metallization buried underthe light reflective resin, silver (Ag) discoloration can be suppressedmore effectively. In addition, the insulating material 107 functions asa passivation layer that can suppress Ag migration. Depending on thestructural materials, the insulating material can also improve adhesionof resin regions such as the light reflective resin 102 to the silver.

To more concretely describe the material constituent of the lightreflective resin, an insulating material is preferable, and a material,which does not easily absorb or transmit light from the light emittingelements or from a source such as external light, is preferable.Further, a material with some degree of strength such as a thermosettingresin or a thermoplastic resin can be used. More specifically, resinssuch as phenol resin, epoxy resin, BT resin, PPA resin, and siliconeresin can be utilized. In these resin bases, powders such as reflectingmaterials (for example, TiO₂, Al₂O₃, ZrO₂, and MgO), which do not easilyabsorb light from the light emitting elements and have a largedifference in index of refraction compared to the resin base, can bedistributed to enable efficient light reflection.

These types of light reflective resins can be formed and patterned usingmethods such as potting methods, printing methods, and direct writingmethods. For example, as shown in FIG. 1A, for the case where lightreflective resin forms a frame surrounding the light emitting elementson an approximately planar substrate, a resin with a somewhat highviscosity can be used to form light reflective resin that afterhardening protrudes from a horizontal plane higher than the lightemitting elements. That resin can be extruded from the tip of a nozzleto form light reflective resin in straight lines. Subsequently, lightreflective resin can be extruded in straight lines perpendicular to thepreviously formed lines to directly write a pattern that forms aplurality of light emitting devices.

(Insulating Material)

Insulating material is provided between the metallization and lightreflective resin, and is established continuously extending over thelight emitting elements. Here, as shown in FIG. 1B and other figures,“established continuously” includes insulating material established inparticulate or needle form over essentially the entire region with somespaces. For example, this includes layers formed from inorganicparticulates by sputter deposition or (physical) vapor deposition.Ingress of gases and moisture etc. that can degrade silver on thesurface of the metallization can be blocked by these insulatingmaterials. Therefore, in a light emitting device with output efficiencyincreased by light reflective resin, silver degradation, which coulddiminish this outstanding result, can be effectively suppressed.Further, as shown in FIG. 1B, by establishing the insulating materialafter connecting the metallization with conducting wire, the insulatingmaterial can also be formed continuously on the conducting wire 105. Inthis manner, adhesion between the conducting wire and the encapsulatingmaterial and the light reflective resin can be improved.

For insulating material, light transparent material is preferable, andprimarily the use of inorganic compounds is desirable. Specifically,oxides such as SiO₂, Al₂O₃, TiO₂, ZrO₂, ZnO₂, Nb₂O₅, MgO, SrO, In₂O₃,TaO₂, HfO, SeO, Y₂O₃, nitrides such as SiN, AlN, AlON, and fluoridessuch as MgF₂ can be utilized. These compounds can be used singly, theycan be mixed, or they can be layered.

With respect to insulating material thickness, a thin layer ispreferable to avoid light loss due to multiple reflections at eachinterface between the encapsulating material, the insulating material,and the metallization. Conversely, a thickness sufficient to block thepassage of gases that include sulfur components is necessary. Althoughthe desirable layer thickness varies somewhat depending on the materialsused, approximately 1 nm to 100 nm is preferable. For the case ofmultiple layers, it is preferable for the total thickness to be withinthis desirable layer thickness range. Further, it is preferable to forma dense layer that makes passage of a gas such as sulfur difficult.

(Substrate)

The substrate is an insulating substance in approximately sheet formthat can have an open cavity in its upper surface, has metallizationdisposed as conductive wiring (conductive runs), and can carry mountedcomponents such as light emitting elements and protection devices.Specifically, materials such as ceramics, epoxy resin, and polyimideresin can be utilized. In particular, by using ceramics as the primarymaterial, a substrate can be made with exceptional ability to withstandheat and environmental conditions.

As ceramics, alumina, aluminum nitride, mullite, silicon carbide, orsilicon nitride can be used. Ceramics can be made with these materialsused as the primary constituents for production. For example, in thecase of alumina, 90-96% by weight alumina can be used as the rawmaterial powder, and approximately 4-10% by weight of a sintering aidsuch as clay, talc, magnesia, calcia, or silica can be added. Thismixture can be sintered in a temperature range of approximately1500-1700° C. to obtain a ceramic for use as a substrate. Or, 40-60% byweight alumina can be used as the raw material powder, and approximately60-40% by weight of a sintering aid such as boro-silicate glass,cordierite, forsterite, or mullite can be added. This mixture can besintered in a temperature range of approximately 800-1200° C. to obtainanother ceramic for use as a substrate.

Further, ceramic powder and binder resin can be mixed to obtain amaterial that can be prepared in sheet-form to produce green sheets. Asubstrate of prescribed shape can be made by laminating and firing thesegreen sheets. Further, ceramic green sheets with through-holes ofvarious sizes can be laminated to make substrates that have cavities. Atthe stage prior to firing the ceramic green sheets, metallization can bedisposed on these types of substrates. Conductive paste that includesmicro-particles of a high-melting-point metal such as tungsten ormolybdenum can be applied to the ceramic green sheet in a prescribedpattern and fired. After firing the ceramic green sheets, the pre-formedmetallization can be plated with a metal such as nickel, gold, orsilver.

Here, for ceramic material substrates, the metallization (conductiveruns) and insulating substrate material (ceramics) can be formed in oneprocess as described above. In addition, metallization can also beformed on pre-fired ceramics in sheet form.

For the case of glass epoxy resin used as a substrate, copper sheet isattached to pre-impregnate half-hardened epoxy resin or glass-clothimpregnated epoxy resin and then thermally hardened. Subsequently, ametallized substrate can be formed by patterning the copper in aprescribed configuration via photolithographic methods.

(Metallization)

In the present embodiment, the metallization is metal containing silver,it is formed on the upper surface of the substrate, it can extendcontinuously to the backside of the substrate through the inside of thesubstrate or via substrate surfaces, and it has the function of makingexternal electrical connection. There are various selections for thesize and pattern of the metallization, and it can be formed in largepatterns to bury the edge regions under light reflective resin 102.Preferably, in a region surrounded by light reflective resin,metallization is provided in a manner that avoids exposure of thesubstrate. Specifically, it is preferable to establish metallizationover the entire surface of the region inside the light reflective resin.In this manner, leakage of light through the substrate, which ismaterial such as a ceramic, to the backside can be suppressed. Further,the metallization includes regions that do not electrically connect tothe outside, but rather function as light reflecting material.Specifically, in addition to metal containing silver, metals such asaluminum, gold, platinum, tungsten, iron, and nickel, as well as alloyssuch as iron-nickel alloy, phosphor bronze, and copper-iron alloy can beutilized. In addition, these metals can be used individually or they canbe used in a plurality of layers. In particular, it is preferable toform a silver-including metal on the surface, and more preferable toform silver plating on the surface.

(Encapsulating Material)

The encapsulating material is material that fills the inside of thecavity (the region surrounded by light reflective resin) and protectsthe electronic components such as the light emitting elements andconducting wire from dust, dirt, moisture, and external forces. Inaddition, the encapsulating material has light transparent properties topass light from the light emitting elements, and preferably has theability to withstand light transmission without easily degrading.Insulating resin composites that are transparent to light from the lightemitting elements such as silicone resin composites, modified siliconeresin composites, epoxy resin composites, modified epoxy resincomposites, and acrylic resin composites are specific examples ofmaterials that can be utilized as the encapsulating material. Inaddition, resins such as silicone resin, epoxy resin, urea resin, fluororesin, and hybrid resins that include at least one or more of theseresins can also be used. Further, encapsulating material is not limitedto these organic compounds, and inorganic materials such as glass andsilica gel can also be used. In addition to these materials, substancessuch as coloring agents, light diffusing agents, filler, and wavelengthconverting agents (fluorescent materials) can be included depending onrequirements. The proper amount of encapsulating material used is anamount that covers the previously mentioned electronic components.

The shape of the surface of the encapsulating material can be selectedfrom various options depending on the desired light distributioncharacteristics. For example, directional characteristics of the lightcan be controlled by forming shapes such as convex lens shapes, concavelens shapes, and Fresnel lens shapes. Further, a lens material that is adifferent material than the encapsulating material can also be provided.

(Die-Bond Material)

The die-bond material is a bonding material for mounting components suchas the light emitting elements and protection devices on the substrateor metallization. Either conductive die-bond material or insulatingdie-bond material can be selected depending on the body (substrate-body)of the active components. For example, in the case of semiconductorlight emitting elements that are nitride semiconductor layers grown onan insulating sapphire substrate-body, either conductive die-bondmaterial or insulating die-bond material can be used. In the case wherea conductive substrate such as SiC is used, electrical connection can bemade by using conductive die-bond material. Bonding materials such asepoxy resin and silicone resin can be used as insulating die-bond. Whenthese types of resins are used, die-bond material degradation due tolight and heat from the light emitting elements is considered and thebackside of the semiconductor light emitting elements can be providedwith a high reflectivity metal such as Al. In this case, methods such asphysical vapor deposition, sputter deposition, or thin film junctiontechniques can be used. Conductive pastes such as silver paste, goldpaste, and palladium paste, or materials such as Au—Sn eutectic solderand low melting point metal brazing material can be used as conductivedie-bond. Further, among these die-bond materials, particularly in thecase where a light transparent die-bond material is used, fluorescentmaterial can be added to absorb light from the light emitting elementsand re-emit light converted to a different wavelength.

(Conducting Wire)

Wire such as gold, copper, platinum, aluminum, and alloys of thesemetals can be utilized as conducting wire to connect light emittingelement electrodes and the metallization (conducting material)established on the substrate. In particular, use of gold wire with itssuperior properties such as thermal resistance is preferable. As shownin figures such as FIG. 1B, conducting wire 105 can be established toconnect continuously between the light emitting elements 104, or theconducting wire can also connect to the conducting material on thesubstrate at each light emitting element.

(Wavelength Converting Material)

In the previously described encapsulating material/lens material,fluorescent material can be included as a wavelength converting materialthat absorbs at least part of the light from the semiconductor lightemitting elements and re-emits light at a different wavelength.

As fluorescent material, materials that convert light from thesemiconductor light emitting elements to a longer wavelength are moreefficient. The fluorescent material can be one type of fluorescentsubstance formed as a single layer, two or more types of fluorescentsubstances mixed and formed as a single layer, two or more layers witheach layer including one type of fluorescent substance, or two or morelayers with each layer including two or more types of fluorescentsubstances mixed together.

For example, the fluorescent material can be wavelength convertingmaterial that absorbs light from semiconductor light emitting elementsthat have nitride-based semiconductor light emitting layers, andconverts that light to a different wavelength. For example, preferablematerials include fluorescent material primarily of activated nitrideand oxide systems of lanthanoide elements such as Eu and Ce, fluorescentmaterial primarily of activated alkaline-earth halogen apatites based onlanthanoide series elements such as Eu and transition-metal elementssuch as Mn, alkaline-earth metal halogen borate fluorescent material,alkaline-earth metal aluminate fluorescent material, and fluorescentmaterial of at least one or more substance selected from analkaline-earth silicate, alkaline-earth sulfide, alkaline-earththiogallate, alkaline-earth silicon nitride, germinate, a materialprimarily of activated rare-earth aluminate of lanthanoide serieselements such as Ce, and a material primarily of activated organic ororganic complex of lanthanoide series elements such as Eu or rare-earthsilicates. Preferably, the material is a YAG fluorescent material thatis primarily an activated rare-earth aluminate of lanthanoide serieselements such as Ce with a chemical formula Y₃Al₅O₁₂:Ce,(Y_(0.8)Gd_(0.2))₃Al₅O₁₂:Ce, Y₃(Al_(0.8)Ga_(0.2))₅O₁₂:Ce, or (Y,Gd)₃(Al, Ga)₅O₁₂. In addition, elements such as Tb and Lu can alsoreplace part or all of the Y component for fluorescent materials such asTb₃Al₅O₁₂:Ce and Lu₃ Al₅O₁₂:Ce. Further, fluorescent materials otherthan those described above with the same performance, function, andeffects as those cited above can also be used.

(Semiconductor Light Emitting Elements)

In the present invention, light emitting diodes are preferably used asthe light emitting elements.

The wavelength of the semiconductor light emitting elements can befreely selected. For example, for blue or green light emitting elements,ZnSe or nitride system semiconductors (In_(X)Al_(Y)Ga_(1-X-Y)N, 0≦X,0≦Y, X+Y≦1) and GaP can be used. For a red light emitting element,systems such as GaAlAs, AlInGaP can be used. In addition, light emittingelements can also be used that are made from materials other than these.The composition, size, and number of light emitting elements employedcan be selected appropriate to the application.

For the case of a light emitting element with fluorescent material, anitride semiconductor (In_(X)Al_(Y)Ga_(1-X-Y)N, 0≦X, 0≦Y, X+Y≦1) thatcan emit short wavelength light is desirable to enable efficientexcitation of the fluorescent material. Various emission wavelengths canbe selected depending on the semiconductor layer materials and thecrystal mix.

In addition to light in the visible range, light emitting elements thatoutput ultraviolet light or infrared light are also possible. Further,light-receiving devices can be mounted together with light emittingelements.

Second Embodiment

The light emitting device 200 of the second embodiment is shown in FIGS.2A, 2B, and 2C. FIG. 2A is an oblique view of the light emitting device200, FIG. 2B is a plan view of the light emitting device 200 shown inFIG. 2A looking through the encapsulating material 206, and FIG. 2C is across-section view through IIC-IIC′ on the light emitting device 200shown in FIG. 2A. In the second embodiment, the light emitting device200 has a substrate 201 provided with cavities having bottom and sidesurfaces, a plurality of light emitting elements 204 mounted onmetallization 203A established on the bottom surface of a cavity,conducting wire 205 to electrically connect metallization 203B and lightemitting elements 204, and encapsulating material 206 that coverscomponents such as light emitting elements 204 and conducting wire 205.The cavities are a first cavity 208 in which the light emitting elements204 are mounted, and second cavities 209 inside the first cavity 208having bottom surfaces positioned below the bottom surface of the firstcavity 208. Light reflective resin 202 is established in a manner thatcovers metallization 203B provided on the bottom surfaces of the secondcavities 209, insulating material 207 is provided between themetallization 203B and the light reflective resin 202, and thatinsulating material 207 is provided extending continuously over thelight emitting elements 204. In this manner, the insulating material 207functions as a passivation layer and Ag migration can be suppressed. Inaddition, depending on the structural materials, the insulating material207 can improve adhesion with resin regions such as the light reflectiveresin 202.

The second embodiment is different from the first embodiment in thatcavities are formed in the substrate. Materials used in the secondembodiment can be the same as those used in the first embodiment. Thefollowing describes in detail aspects of the second embodiment that aredifferent from the first embodiment.

(Cavities)

In the light emitting device 200 of the second embodiment, the cavitiesare a first cavity 208 in which the light emitting elements are mounted,and second cavities 209 inside the first cavity 208 having bottomsurfaces positioned below the bottom surface of the first cavity 208.The following describes the cavities in detail.

(First Cavity)

The first cavity has metallization established on its bottom surface andlight emitting elements are mounted on top of that metallization.Further, the light emitting device has second cavities with bottomsurfaces positioned lower than the bottom surface of the first cavity.In other words, the cavities of this embodiment are formed in twolevels, and second cavities with a smaller cavity opening size areformed inside the first cavity with a large cavity opening size.

The bottom surface of the first cavity should be large enough toallocate area required to mount the light emitting elements in a regionoutside the second cavities. The bottom surface of the first cavityshould have a continuous region with an area greater than the area ofthe bottom surfaces of the light emitting elements to avoid mounting alight emitting element coincident with a second cavity (overlapping orcovering a second cavity). For example, nine light emitting elements 204are mounted in the light emitting device 200 of FIG. 2B, and the firstcavity has a bottom surface with an area that allows all nine lightemitting elements 204 to be mounted. In the case where a plurality oflight emitting elements is mounted, it is preferable to mount all thelight emitting elements on a continuous piece of metallization. In thecase where light emitting elements are mounted on other materials suchas submounts, the bottom surface of the first cavity should have an areathat allows the submounts to be attached. It is also possible to providea plurality of first cavities. For example, two first cavities can beprovided with light emitting elements mounted in each cavity, and secondcavities can be provide in each first cavity.

Metallization established on the bottom surface of the first cavity canbe used as an electrode lead to supply electric power to the lightemitting elements. Or, the metallization can be used not to conductelectricity, but rather to improve light reflectivity and heat transfer.

In particular for the case where ceramics are used as the substrate, itis preferable to establish metallization over the entire bottom surfaceof the first cavity (the entire surface excluding second cavityregions). In this manner, exposure of the substrate can be avoided, andleakage of light can be reduced. For example, as shown in FIG. 2B,metallization 203A is established on essentially the entire bottomsurface of the first cavity 208. Here, conducting wire 205 is connectedto metallization 203B on the bottom surfaces of the second cavities 209,and these (conducting material) metallization 203B regions are used aselectrodes. Metallization 203A on the bottom surface of the first cavitydoes not contribute to electrical conduction and is primarily used asreflecting material to efficiently reflect light.

The shape of the bottom surface of the first cavity is not limited tothe approximately square shape shown in FIG. 2B and can have anarbitrary shape such as circular or elliptical. Similarly, the cavityopening at the top of the cavity can also have an arbitrary shape. Here,although the shape of the bottom surface of the first cavity and theshape of the cavity opening are similar, similar shapes are not alwaysnecessary and the bottom surface and the opening of the cavity can havedifferent shapes. For example, the shape of the bottom surface of thecavity can be approximately square and the shape of the cavity openingcan be approximately circular.

The side-walls of the first cavity can be perpendicular to, or inclinedwith respect to the bottom surface, and the first cavity side-walls canbe provided continuous with segments of the second cavity side-walls.Further, as shown in FIG. 2C, the second cavities can be established inpositions essentially connecting with the side-walls of the first cavityor forming steps with respect to the side-walls of the first cavity. Inaddition, metallization can be established on the side-walls of thefirst cavity 208.

(Second Cavities)

The second cavities are cavities formed inside the first cavity, and thesecond cavities have bottom surfaces disposed below the bottom surfaceof the first cavity. In the second embodiment, metallization isestablished on the bottom surfaces of the second cavities, and theinsides of the second cavities are filled with light reflective resin.Insulating material is disposed between the metallization and the lightreflective resin and that insulating material extends continuously overthe light emitting elements.

Metallization established on the bottom surfaces of the second cavitiesserve as electrodes to supply power to the light emitting elements. Themetallization is embedded along with part of the conducting wires insidethe light reflective resin. Metallization can be established as a pairof positive and negative electrodes as shown in FIG. 2B or as either apositive or negative electrode inside one second cavity or inside eachof a plurality of second cavities. In the case where metallization isestablished inside a second cavity as either a positive or negativeelectrode, the other electrode can be metallization established on thebottom surface of the first cavity or it can be metallizationestablished on the bottom surface of another second cavity. In addition,one polarity of the conducting wire from the light emitting elements canbe connected to metallization established on the bottom surface of thefirst cavity (positive electrode), and the other polarity can beconnected to second cavity metallization (negative electrode) toimplement electrical connection.

One, or two or more second cavities can be provided in the bottomsurface of the first cavity, and the second cavity openings are formedwith sizes that do not interfere with mounting the light emittingelements. Second cavities can be disposed in arbitrary locations. Forexample, as shown in FIG. 2B, second cavities 209 with elliptical cavityopenings can be provided along each of two sides of the approximatelysquare bottom surface of the first cavity 208 for a total of two secondcavities 209. Here, the two second cavities are the same size and shape,and, as shown in FIG. 2B, are located in symmetrical positions. However,second cavities are not limited to this configuration and secondcavities can have different cavity opening areas and different sizes,etc. Further, although metallization 203B is established in all of thesecond cavities 209, all of the metallization does not necessarily havebe used for electrical conduction.

As shown in FIG. 2B, when a protection device 210 is mounted inside asecond cavity 209, second cavity bottom surface and metallization areais required that is greater than the area of the bottom surface of theprotection device 210. Further, in the case of conducting wire 205attachment, the cavity opening must be wide enough to allow wire-bondingtool access inside the cavity.

(Metallization)

In the second embodiment, metallization is established on the bottomsurface of the first cavity and on the bottom surfaces of the secondcavities. In particular, it is preferable to establish metallizationover essentially the entire bottom surface of the first cavity toprevent light from entering the substrate and to reduce light loss. Inthis case, metallization on the bottom surface of the second cavitiescan be used as a pair of electrodes, metallization established on thebottom surface of the first cavity does not have to function as anelectrode, and that first cavity metallization can function simply as ahigh reflectivity material or high-quality heat transfer material.Degradation of this metallization, which is established over a widearea, can be suppressed by covering it with an insulating material thatis essentially impermeable to gas. As desirable insulating materials,materials that are the same as those cited for the first embodiment canbe utilized. Metallization 203A established in the first cavity andmetallization 203B established on the bottom surfaces of the secondcavities can be the same material, or preferably, they can be separatematerials. Specifically, metallization 203A established in the firstcavity in a location that is illuminated by much of the light from thelight emitting elements preferably has silver or metals including silveron its surface, and in particular, silver is preferable.

As shown in FIG. 2C, the light reflective resin for the secondembodiment fills the inside of the second cavities 209. The lightreflective resin fills the second cavities 209 in a manner that hasconcave curved surface cross-sections and is established extending tothe top of the first cavity side-walls, namely, to the upper surface ofthe substrate 201. Consequently, leakage of light through the substrate201 can be prevented. This configuration of light reflective resin canbe formed by relatively simple techniques by applying a prescribedamount of liquid resin with adjusted viscosity in the second cavities ofthe substrate to spontaneously spread the liquid resin over the sidewalls of the cavities.

It is preferable for the light reflective resin to cover not only thebottom surfaces of the second cavities but also essentially the entireside-wall surfaces. It is also preferable for the light reflective resinto cover most of the first cavity side-walls. Further in the case of aplurality of second cavities and, for example, in the case where thesecond cavities are separated as shown in FIG. 2B, it is preferable toform light reflective resin that fills the second cavities continuouslyacross the bottom surface of the first cavity. In addition, thatcontinuously formed light reflective resin also preferably extends fromthe bottom surface of the first cavity to the top surface of thesubstrate. Here, the light reflective resin on the side-walls of thesecond cavities can be a thickness that allows light from the lightemitting elements to be reflected (not transmitted easily). A minimumlayer thickness can be specified according to the light transmissivityof the light reflective resin material. Further, light reflective resinlayer thickness does not have to be the same over the entire side-wallsof the second cavities. For example, layer thickness can graduallybecome thinner towards the top of a second cavity side-wall. The samelight reflective resin materials cited for the first embodiment can beproposed as specific examples of materials to form the light reflectiveresin for this embodiment.

(Insulating Material)

In the same manner as the first embodiment, the second embodiment alsohas insulating material established between the light reflective resinand metallization, and that insulating material extends continuouslyover the light emitting elements. As shown in FIG. 2C, the insulatingmaterial is formed on the side-walls of the first cavity and on theside-walls of the second cavities, and is also established on the uppersurface of the substrate 201. Here, dense insulating material, which isessentially impermeable to gas, covers the surfaces of the substrate,which is made from relatively porous materials such as ceramics.Consequently, gas ingress from the side and upper surfaces of thesubstrate as well as from the encapsulating material 206 can besuppressed. Often it is difficult to form insulating material with thesame uniform thickness on the bottom and side surfaces of the secondcavities and on the bottom surface of the first cavity. For example, fordry process methods such as sputter deposition and physical vapordeposition, regions inside the second cavities can easily become thindue to shadow effects. Conversely, for wet process methods employingliquid coating, cracking and delamination can occur in regions that aretoo thick due to liquid pooling. However, since the second cavities arefilled with light reflective resin, it is not always necessary to forminsulating material over the entire inside regions of the secondcavities. Assuming metallization in the second cavities is a metalincluding silver (silver plating), there is no effect even when metaldiscoloration occurs because of the light reflective resin.Consequently, the most convenient method of forming the insulatingmaterial should be chosen from the various methods available.

Third Embodiment

FIG. 3 shows a cross-section view of a light emitting device 300 for thethird embodiment. The external appearance of the light emitting device300 is similar in form to the light emitting device 100 shown in FIG.1A, and the difference is the location where the insulating material 307is formed. Specifically, the light emitting device of the thirdembodiment has a substrate 301 with metallization 303 (303A, 303B, 303C)that has metal including silver on its surface, light emitting elements304 mounted on the substrate, conducting wire 305 that electricallyconnects metallization 303B and light emitting elements 304,encapsulating material 306 that fills the cavity surrounded by lightreflective resin 302, light reflective resin 302 established on top ofthe substrate 301 to reflect light emitted by the light emittingelements 304, and insulating material 307 established on top of thelight reflective resin 302. The insulating material 307 is establishedextending continuously over the light emitting elements 304. With thisconfiguration, degradation of silver plating on the metallization can besuppressed, and the insulating material 307 can function as apassivation layer to suppress Ag migration. Further, depending on thecomponent materials, adhesion of resin regions such as the lightreflective resin 302 regions can be improved. In addition, even whenresins that easily degrade or become discolored due to oxidation areused as bulk resins for the light reflective resin in particular, theinsulating material 307 blocks oxygen ingress and degradation ordiscoloration of the light reflective resin 302 can be suppressed.

Forth Embodiment

FIG. 4 shows a cross-section view of a light emitting device 400 for thefourth embodiment. The external appearance and internal structure of thelight emitting device 400 is similar in form to the light emittingdevice 200 shown in FIGS. 2A and 2B, and the difference is the locationwhere the insulating material 407 is formed. Specifically, the lightemitting device of the fourth embodiment has a substrate 401 withmetallization 403 (403A, 403B) that has metal including silver on itssurface, light emitting elements 404 mounted on the substrate,conducting wire 405 that electrically connects metallization 403B andlight emitting elements 404, and encapsulating material 406 that fillsthe cavity surrounded by light reflective resin 402. Cavities include afirst cavity 408 where light emitting elements 404 are mounted andsecond cavities 409 inside the first cavity 408 having bottom surfacesthat are positioned lower than the bottom surface of the first cavity.Light reflective resin 402 is provided covering metallization 403Bestablished on the bottom surfaces of the second cavities 409,insulating material 407 is provided on the surface of that lightreflective resin 402, and that insulating material 407 extendscontinuously over the light emitting elements 404. With thisconfiguration, degradation of silver plating on the metallization can besuppressed, and the insulating material 407 can function as apassivation layer to suppress Ag migration. Further, depending on thecomponent materials, adhesion of resin regions such as the lightreflective resin 402 regions can be improved. In addition, even whenresins that easily degrade or become discolored due to oxidation areused as bulk resins for the light reflective resin in particular, theinsulating material 407 blocks oxygen ingress and degradation ordiscoloration of the light reflective resin 402 can be suppressed.

Fifth Embodiment

FIG. 5 shows a cross-section view of a light emitting device 500 for thefifth embodiment. The external appearance of the light emitting device500 is similar in form to the light emitting device 100 shown in FIG.1A, and the difference is the location where the insulating material isformed. Specifically, the light emitting device of the fifth embodimenthas a substrate 501 with metallization 503 (503A, 503B, 503C) that hasmetal including silver on its surface, light emitting elements 504mounted on the substrate, conducting wire 505 that electrically connectsmetallization 503B and light emitting elements 504, encapsulatingmaterial 506 that fills the cavity surrounded by light reflective resin502, light reflective resin 502 established on top of the substrate 501to reflect light emitted by the light emitting elements 504, andinsulating material 507 established between the metallization 503 andthe light reflective resin 502. The insulating material 507 isestablished continuously extending to contact the sides of the lightemitting elements 504. In the fifth embodiment, the insulating materialis not established on top of the light emitting elements, but rather isestablished to come in contact with the sides of the light emittingelements. With this configuration, degradation of silver plating on themetallization can be suppressed, and the insulating material 507 canfunction as a passivation layer to suppress Ag migration. Further,depending on the component materials, adhesion of resin regions such asthe light reflective resin 502 regions can be improved.

Sixth Embodiment

FIG. 6 shows a cross-section view of a light emitting device 600 for thesixth embodiment. The external appearance and internal structure of thelight emitting device 600 is similar in form to the light emittingdevice 200 shown in FIGS. 2A and 2B, and the difference is the locationwhere the insulating material 607 is formed. Specifically, the lightemitting device of the sixth embodiment has a substrate 601 withmetallization 603 (603A, 603B) that has metal including silver on itssurface, light emitting elements 604 mounted on the substrate,conducting wire 605 that electrically connects metallization 603B andlight emitting elements 604, and encapsulating material 606 that fillsthe cavity surrounded by light reflective resin 602. Cavities include afirst cavity 608 where light emitting elements 604 are mounted andsecond cavities 609 inside the first cavity 608 having bottom surfacesthat are positioned lower than the bottom surface of the first cavity.Light reflective resin 602 is provided covering metallization 603Bestablished on the bottom surfaces of the second cavities 609,insulating material 607 is provided between the metallization 603B andthe light reflective resin 602, and that insulating material 607 extendscontinuously to contact the sides of the light emitting elements 604. Inthe sixth embodiment, the insulating material is not established on topof the light emitting elements, but rather is established to come incontact with the sides of the light emitting elements. With thisconfiguration, degradation of silver plating on the metallization can besuppressed, and the insulating material 607 can function as apassivation layer to suppress Ag migration. Further, depending on thecomponent materials, adhesion of resin regions such as the lightreflective resin 602 regions can be improved.

INDUSTRIAL APPLICABILITY

The light emitting device and method of manufacture according to thepresent invention has a structure that makes it difficult for light toleak from the substrate, thereby reducing light loss and allowingrealization of a light emitting device that makes higher outputspossible. These light emitting devices can be used in applications suchas in various indicator apparatus, lighting equipment, display monitor,backlight source for a liquid crystal display, image acquisitionapparatus such as facsimile, copier, and scanner apparatus, andprojector apparatus.

It should be apparent to those with an ordinary skill in the art thatwhile various preferred embodiments of the invention have been shown anddescribed, it is contemplated that the invention is not limited to theparticular embodiments disclosed, which are deemed to be merelyillustrative of the inventive concepts and should not be interpreted aslimiting the scope of the invention, and which are suitable for allmodifications and changes falling within the spirit and scope of theinvention as defined in the appended claims.

The present application is based on Application No. 2009-019412 filed inJapan on Jan. 30, 2009, and No. 2009-268587 filed in Japan on Nov. 26,2009, the contents of which are incorporated herein by references.

1. A light emitting device comprising: a substrate; metallization provided on the surface of the substrate that has metal including silver; a light emitting element mounted on the substrate; conducting wire that electrically connects the metallization and the light emitting element; light reflective resin provided on the substrate to reflect light from the light emitting element; and insulating material that covers at least part of the metallization surfaces; wherein the insulating material is established to come in contact with the side of the light emitting element.
 2. The light emitting device as cited in claim 1 wherein the substrate has cavities with bottom and side surfaces; the cavities include a first cavity where light emitting element is mounted, and second cavities inside the first cavity having bottom surfaces positioned lower than the first cavity; and the light reflective resin is established on metallization inside the second cavities.
 3. The light emitting device as cited in claim 2 wherein the insulating material covers side-walls of the second cavities that connect with the first cavity.
 4. The light emitting device as cited in claim 2 wherein the light reflective resin extends upwards from the second cavities to a position above the bottom surface of first cavity.
 5. A light emitting device comprising: a substrate; metallization provided on the surface of the substrate that has metal including silver; a light emitting element mounted on the substrate; conducting wire that electrically connects the metallization and the light emitting element; light reflective resin provided on the substrate to reflect light from the light emitting element; and insulating material that covers at least part of the metallization surfaces; wherein the insulating material is established continuously over metallization surfaces and on the upper surface of the light emitting element.
 6. The light emitting device as cited in claim 5 wherein the insulating material is established intervening between the metallization and the light reflective resin, and the insulating material extends continuously over the upper surface of the light emitting element.
 7. The light emitting device as cited in claim 5 wherein the insulating material is established on the surface of the light reflective resin, and the insulating material extends continuously over the upper surface of the light emitting element.
 8. The light emitting device as cited in claim 1 wherein the insulating material is established to cover the surfaces of conducting wire continuously from the upper surface of the light emitting element.
 9. The light emitting device as cited in claim 1 wherein the insulating material covers essentially the entire upper surface of the substrate.
 10. The light emitting device as cited in claim 1 wherein encapsulating material is provided on the upper surface of the substrate to encapsulate the light emitting element, essentially all surfaces of the conducting wire, and at least part of the insulating material.
 11. The light emitting device as cited in claim 1 wherein the insulating material has light transparency.
 12. The light emitting device as cited in claim 1 wherein the insulating material is an inorganic compound.
 13. The light emitting device as cited in claim 1 wherein the insulating material is SiO₂.
 14. The light emitting device as cited in claim 1 wherein the light emitting element is mounted on the metallization, and the metallization functions as an electrode.
 15. A method of manufacturing a light emitting device, the method comprising: providing a substrate that has a first cavity, and second cavities inside the first cavity with bottom surfaces positioned below the first cavity; establishing metallization on the upper surface of the substrate; providing a light emitting element on top of the metallization, and connect the metallization and light emitting element with conducting wire; covering continuously with insulating material the surfaces of metallization on the bottom surfaces inside the second cavities, the side-walls that join with the first cavity, the surface of metallization in the first cavity, surface of the light emitting element, and the conducting wire; and providing light reflective resin in the second cavities to reflect light from the light emitting element. 